WU Chao fan, CHEN Long dao

 

(College of Electrical Engineering, Zhejiang Universing, Hangzhou, 310027)

 

 

Abstract: Aiming at the problem that traditional harmonic measurement methods based on FFT lead to a larger error in the measurement of the harmonic signal in power grid, especially the time varying signal such as unsteady periodic signal and so on. A method of time domain interpolation was used to synchronize the asynchronous sampling signal. First of all, zero crossing detection was used to determine the actual frequency of the signal and reposition the ideal sampling sequence according to the the ideal sampling interval, then the signal was synchronized by applying Hermite interpolation algorithm on the actual sampling value. Finally, the spectrum of signal would be analyzed with the help of FFT transform. The calculation was proceded in two situations of the fundamental frequency offset is fixed and fundamental frequency is fluctuating. The results indicate that hermite interpolation synchronization algorithm can be applied to the above two cases. Taking computational efficiency into account, it can meet the accuracy requirement of GBT 17626.7—2008 at the same time. The Hermite interpolation synchronization algorithm is a kind of practical method.

 

Key words: asynchronous sampling; synchronization algorithm; hermite interpolation algorithm